如果你只想使用内置程序，最简单的方法可能是:

find `pwd` -name fileName

只需多输入两个字，就可以在所有unix系统和OSX上工作。

find命令可能有帮助

find $PWD -name ex*
find $PWD -name example.log

列出名称与模式匹配的当前目录中或下面的所有文件。你可以简化它，如果你只会得到几个结果(例如，目录接近树的底部包含几个文件)，只是

find $PWD

我在Solaris 10上使用这个工具，Solaris 10没有提到的其他实用程序。

用Homebrew回答

Realpath是最好的答案，但如果你没有安装它，你必须首先运行brew install coreutils，它将安装coreutils与许多很棒的功能。编写一个自定义函数并导出它是太多的工作和错误的风险，对于这样的东西，这里有两行:

$ brew install coreutils
$ realpath your-file-name.json 

在某些情况下，这个问题最上面的答案可能具有误导性。假设你要查找的文件的绝对路径在$ path变量中:

# node is in $PATH variable
type -P node
# /home/user/.asdf/shims/node
cd /tmp
touch node  # But because there is a file with the same name inside the current dir check out what happens below
readlink -e node
# /tmp/node
readlink -m node
# /tmp/node
readlink -f node
# /tmp/node
echo "$(cd "$(dirname "node")"; pwd -P)/$(basename "node")"
# /tmp/node
realpath node
# /tmp/node
realpath -e node
# /tmp/node

# Now let's say that for some reason node does not exist in current directory
rm node
readlink -e node
# <nothing printed>
readlink -m node    
# /tmp/node         # Note: /tmp/node does not exist, but is printed
readlink -f node
# /tmp/node         # Note: /tmp/node does not exist, but is printed
echo "$(cd "$(dirname "node")"; pwd -P)/$(basename "node")"
# /tmp/node         # Note: /tmp/node does not exist, but is printed
realpath node
# /tmp/node         # Note: /tmp/node does not exist, but is printed
realpath -e node
# realpath: node: No such file or directory

基于以上，我可以得出结论:realpath -e和readlink -e可以用于查找文件的绝对路径，我们期望存在于当前目录中，而不受$ path变量的影响。唯一的区别是realpath输出到stderr，但如果没有找到file，两者都会返回错误代码:

cd /tmp
rm node
realpath -e node ; echo $?
# realpath: node: No such file or directory
# 1
readlink -e node ; echo $?
# 1

现在，如果您想要一个存在于$ path中的文件的绝对路径a，那么下面的命令将是合适的，这与当前目录中是否存在同名文件无关。

type -P example.txt
# /path/to/example.txt

# Or if you want to follow links
readlink -e $(type -P example.txt)
# /originalpath/to/example.txt

# If the file you are looking for is an executable (and wrap again through `readlink -e` for following links )
which executablefile
# /opt/bin/executablefile

如果没有，回退到$PATH，示例:

cd /tmp
touch node
echo $(readlink -e node || type -P node)
# /tmp/node
rm node
echo $(readlink -e node || type -P node)
# /home/user/.asdf/shims/node

对于目录，dirname将为../并返回。/。

Nolan6000的函数可以修改来修复这个问题:

get_abs_filename() {
  # $1 : relative filename
  if [ -d "${1%/*}" ]; then
    echo "$(cd ${1%/*}; pwd)/${1##*/}"
  fi
}

#! /bin/bash

file="$@"
realpath "$file" 2>/dev/null || eval realpath $(echo $file | sed 's/ /\\ /g')

这弥补了realpath的缺点，将它存储在shell脚本fullpath中。你现在可以调用:

$ cd && touch a\ a && rm A 2>/dev/null 
$ fullpath "a a"
/home/user/a a
$ fullpath ~/a\ a
/home/user/a a
$ fullpath A
A: No such file or directory.